The present invention relates generally to liquid containing compositions and transport or pumping thereof, which compositions achieve maximum fluid friction reduction properties at low concentrations of a drag reducing agent, such as less than 0.015% by weight and preferably less than 0.01% by weight of a drag reducing polymer of 2-acrylamido-2-methylpropanesulfonic acid, or soluble salts thereof.
In U.S. Pat. No. 3,931,089 there is disclosed the use of polymeric 2-acrylamido-2-methylpropanesulfonic acid as a thickener for acid solutions which find utility in acidizing of oil wells. The thickening polymer is employed in amounts of 0.05-5.0%, generally about 1-4%, by weight. Reference is also made to the use of certain alcohols as stabilizers.
In U.S. Pat. No. 4,332,688 the use of oxyalkylated acrylamido alkanesulfonic acid polymers in aqueous solution of acids is disclosed for thickening and facilitating flow in the subterranean hydrocarbon-bearing formation. The polymer is employed in an amount of about 0.5 to about 5% by weight.
Again, in U.S. Pat. No. 4,107,057 well acidizing or fracturing compositions are disclosed using a cross-linked sulfonic acid modified acrylamide, 25-100 pounds per 1,000 gallons of base fluid.
U.S. Pat. Nos. 4,242,098 and 4,375,358 relate to the transport of slurries of solid materials, particularly of carbonaceous materials such as coal, in aqueous systems using a variety of water soluble polymers at levels of 0.05-5.0%, and generally 0.3-1.0%, by weight. Among such polymers are included poly(ethylene)oxide, partially hydrolyzed polyacrylamide, cellulose derivatives and gums such as xanthan gum and guar derivatives.
U.S. Pat. Nos. 4,065,422 and 4,128,631 relate to the use of acrylamide alkyl sulfonic acid polymers in personal care products which may be used in keratinous substrates such as skin or hair. While not relating to transport or pumping of materials such as contemplated by the present invention, the patent does describe "high slip" properties and a high degree of lubricity in the personal care products which employ alcohol as a carrier or solvent therefor. The polymer is employed in an amount preferably of 0.1-10% by weight, but a general range of 0.01-50% is disclosed.
As can be seen from the foregoing, the acrylamide alkane sulfonic acid polymers have been used in the past generally as thickeners for aqueous solutions employed in subterraneous formations in oil and gas recovery operations. In such operations, large amounts of an aqueous composition are employed which must be pumped and transported requiring high amounts of energy to pump the fluid, particularly with thickened compositions. In such applications, the phenomenon of "drag reduction" or "friction reduction" is economically important because it lowers the energy required to pump a fluid at a given rate or it permits the fluid to be pumped faster at the same energy input. Such energy savings are of course desirable in transportation or pumping of liquids, either by themselves or where used as carriers for other materials in finely divided form. Drag reduction can be defined as the increase in the ease of pumpability of a fluid caused by the addition of small amounts of another substance to the fluid. During drag reduction, the fluid containing the additive requires a lower pressure gradient to move it at a given mean velocity in a pipe than the same fluid without the additive. Although a large number of experimental studies have been carried out to investigate this phenomenon of drag reduction, the exact mechanism is not well understood. Many researchers do agree, however, that drag reduction is caused by some kind of interaction between turbulent eddies and the dissolved polymers near the pipe walls, N. D. Sylvester and J. S. Tyler, Ind. Eng. Chem. Prod. Res. Develop., Vol. 9, No. 4, 1980, p. 548.
Extensive use of drag reduction additives is being made in petroleum production operations, particularly in fracturing processes where fluids are pumped at high pressures and flow rates. Other promising applications for drag reduction additives are in ship hull friction reduction, in pipelines, in fire fighting hoses, in water and sewer systems, and in sprinkler irrigation systems.